The fastest growing “religious” group in America is made up of people with no religion at all, according to a Pew survey showing that one in five Americans is not affiliated with any religion.

The number of these Americans has grown by 25% just in the past five years, according to a survey released Thursday by the Pew Forum on Religion and Public Life.

The survey found that the ranks of the unaffiliated are growing even faster among younger Americans.

Thirty-three million Americans now have no religious affiliation, with 13 million in that group identifying as either atheist or agnostic, according to the new survey.

Pew found that those who are religiously unaffiliated are strikingly less religious than the public at large. They attend church infrequently, if at all, are largely not seeking out religion and say that the lack of it in their lives is of little importance.